Hitherto, in the field of paints, the conversion from organic solvent-based paints to water-based paints has been attempted from the viewpoint of environmental conservation and safety and health. However, the water-based paints have a problem that the appearance of coating film and the coating film performance such as weather resistance, water resistance, solvent resistance, and contamination resistance are poorer as compared with those of the organic solvent-based paints.
Hence, paints containing an intraparticle mixture of resins having different properties have been proposed in order to solve these problems.
For example, in Patent Documents 1 and 2, a particulate polymer as a mixture of a urethane resin and an acrylic polymer obtained by emulsion polymerization of an acrylic monomer in an aqueous dispersion of the urethane resin is described.
In addition, Patent Document 3 also describes a particulate polymer using a urethane resin and an acrylic polymer.
In addition, it is recently required to dry the paint at a low temperature in a short time in the drying step after coating from the viewpoint of energy saving. Hence, a paint exhibiting water resistance and solvent resistance under such a drying condition is required.